Power-assisted operating mechanism for hydraulic pressure systems



Jan. 24, 1961 Original Filed Nov. 21,

ANDOL G. T. R POWER-ASSISTED OPERATING MECHANISM FOSR HYDRAULIC PRESSURESYSTEMS 4 Sheets$heet 1 G. T. RANDOL POWER-ASSISTED 0 Jan. 24, 19612,968,926

7 PERATING MECHANISM FOR HYDRAULIC PRESSURE SYSTEMS Original Filed Nov.21, 1955 4 Sheets-Sheet 2 invemar 1961 G. T. RANDOL POWER-ASSISTEDOPERATING MECHANISM FOR HYDRAULIC PRESSURE SYSTEMS 4 Sheets-Sheet}'Original Filed Nov. 21, 1955 Jan. 24, 1961 G T RANDQL 2,968,926

POWER-ASSISTED OPERATING MECHANISM FOR HYDRAULIC PRESSURE SYSTEMSOriginal Filed NOV. 21, 1955 4 Sheets-Sheet 4 as: F3 266 c 7 Gc f B n290 a 3 z N Z /.?/r: H02 7 33 292 2/02 40 27a mic /2/z an '5 f f H use/66 223a TIE: 1 1

(\Z'A @QWAW/l/ll/ZQIAL l l% Inventor POWER-ASSISTED OPERATING MECHANISMFOR HYDRAULIC PRESSURE SYSTEMS Glenn T. Randol, Mountain Lake Park, Md,assignor of fifty I\plerflent to Hamill-Markus Industries, Inc., Warren,1c

Original application Nov. 21, 1955, Ser. No. 547,994. and thisapplication Jan. 24, 1957, Ser. No.

12 Claims. (Cl. 6054.6)

The present invention relates to power-assisted operating mechanism inwhich physical operating force applied to an operator-operated member issupplemented by power assistance, said mechanism including a liquidpressure producing device which is intended primarily as an actuator forhydraulic brake systems of automotive vehicles and the like, althoughother uses are obviously feasible. This application is a division of mycopending application Serial No. 547,994, filed November 21, 1955.

The present invention has for a broad objective, the provision of a newand novel power control valve for controlling the pressure-responsivepower assembly of a pressure-differential operated booster motor, saidcontrol valve having at least two principal relative displaceablespring-loaded elements with included spring-reaction progressivelytransmitted to an operator-operated member via one of the valve elementsmechanically connected directly to said opera-tor member, duringpower-boost; said spring-loaded valve elements being opposed by saidspringreaction supplemented by hydraulic reaction upon the fluid in themaster cylinder becoming pressurized whereby relative displacementaforesaid of said valve elements is induced when operator force exertedon the one valve element exceeds the forcetransmitting capacity of thenormally preloaded status of said valve elements substantiallycounterbalanced by said opposing spring and hydraulic reaction on thefluid-displacing assembly in the master cylinder.

An object related to the object next above is the provision of new andnovel interaction and cooperation be tween the fluid-displacing assemblyof the conventional firewall mounted master cylinder and the saidcontrol valve whereby said booster motor attains its operative status toproduce power-boost in response to said relative displacement of thevalve elements accommodated by modulation of their normallyspring-loaded status induced by reaction from the master cylinder returnspring reacting on said fluid-displacing assembly subsequentlysupplemented by hydraulic reaction thereagainst when the brake fluidbecomes initially pressurized in accord ance with thethrust-transmitting capacity of the normal spring load on said valveelements under influence of said operator member.

Another object related to the two objects immediately preceding is toprovide a booster brake assembly of the above character whereinconditioning of the brake master cylinder to pressurize the brake fluidis effected in response to initial movement of the operator member froma normally released position prior to relative displacement thereby ofsaid control valve elements for power-activation of said booster motor.

The prior art discloses a pressure producing device comprising asubstantially conventional master cylinder, a power cylinder, and twocoaxial plunger or piston members adapted to concurrently displaceliquid from the master cylinder, one of said members being operablyprojectable into the master cylinder by the .power cylinder movablemember, and the other of said members being 2,968,926 Patented Jan. 24,l6i

operably projectable relatively to and simultaneously with the onemember by the force exerted by the operator on a member such as a pedal.

The primary object of the present invention is to provide a device ofthis type which is appreciably improved from the standpoint ofcommercial acceptability over any similar device heretofore proposed.Such improve ment providing the following advantages:

(:1) Improved reaction on the operator pedal member to provide anunusually controllable power-boost to give the pedal a natural live feelwith instinctive predictable braking reaction;

([1) A power unit which utilizes the conventional footoperated mastercylinder without sacrificing its well known and desirable features ofliquid compensation to maintain the hydraulic system in brake-applyingcondition, the most simple and effective method of sealing the liquidwithin the pressure chamber from the power chamber of the power unit,and the especially important operating characteristic of enablingfeathering of the brake-applying operation as by pumping the pedal tomaintain brake shoe contact as expansion of the brake drum occurs onlong downgrades, and to prevent overheating resulting from the necessityof sustained brake shoe contact as in prior art devices devoid of liquidcompensation at all working positions of the pedal;

(c) A power unit in which the pressure-transmitting member actuated bythe movable power member is directly operated by the pedal in the normalmanner independently of the power member when power is ofi to provide astraight-through operation of the convention-al master cylinder;

(d) A power unit combining hydraulic and spring reaction progressivelyincreased as the pedal is moved from released position with such springreaction removed from the power member during brake-applying and holdingoperations to provide maximum power-boost at all energized positions ofthe power member;

(e) A power-operated master cylinder which requires no learning periodor change of driver habits, and literally improves the safety of caroperation over that provided with foot-operated hydraulic brakingsystems;

(f) A power unit which incorporates control valving coaxially disposedwholly within the tubular pressuretransmitting member aforesaid toprovide a most simple and durable power control arrangement; and

(g) A power unit requiring a small diameter cylinder to facilitateinstallation in present-day motor cars in which space is at a premiumespecially for accessories incorporated in the engine compartment onafter-market cars.

Stated in greater detail, the present invention provides novelpower-operated means disposed between a hydraulic master cylinder ofsubstantially conventional design and the associated driver-operatedpedal, for controlling in part braking operations and transmitting tothe driver via said pedal an awareness, or physical perception, of aportion of the total brake-applying hydraulic thrust engendered inresponse to incremental depressing and releasing movements of the pedalaforesaid for causing corresponding operations substantially of thepower-operated means to assist in the actuation of the hydraulic mastercylinder to apply and release the brakes, respectively, said hydraulicthrust reaction being supplemented by spring means characterized byincreasing tension on the pedal progressively induced by operation ofthe pedal in a brake-applying direction from released position.

The assembly referred to in the preceding paragraph incorporates a novelarrangement of the parts whereby the piston of the hydraulic mastercylinder is tubular and includes a coaxially disposed piston of lesscross-sectional area operably connected to the pedal via a controlelement 6 for controlling the operating power to energize thepoweroperated means, said latter piston providing proportional hydraulicthrust on the pedal to the degree of total braking force effective inthe hydraulic lines. The master cylinder piston assembly being ofcomposite arrangement comprising the two pistons aforesaid with thetubular piston acted on by the movable power assembly of thepoweroperated means, and the smaller coaxial piston is operablyconnected to the pedal via the control element for the power-operatedmeans, said latter connection providing limited relative movement of thepedal, control element and piston of less cross-sectional area withrespect to the tubular piston with both of said pistons operablyprojectable into the hydraulic pressure chamber. The movable powerassembly is mounted on the tubular piston in encircling relationshipwith respect thereto and is optionally detachable from or fixed to saidtubular piston enabling pedal operation of the tubular pistonindependently of or in unison with the movable power member in the eventof power failure or inadequacy. In the latter instance increasedphysical effort on the pedal would be required due to the addedresistance of the movable power assembly and its return spring acting inopposition to pedal operation thereof when the power is off.

A further object importantly related to the object immediately precedingis the novel operative association of normally preloaded spring meansbetween a conventional residual pressure check-valve and thepedal-actuated piston section for producing the aforesaid supplementalreaction characterized by increasing tension progressively induced bypedal operation in a brake-applying direction, said spring meansincluding a movable seat continuously acting on the aforesaid pistonsection exposed to the hydraulic thrust within the master cylinderpressure chamber whereby the spring means react so ely on the pedal viathe coaxial piston and control element during power assistance, butrelease of the pedal is effective to cause the movable seat underinfluence of said spring means. to engage the tubular piston Withresultant simultaneous movement of both pistons and control elementaforesaid to their respective released positions wherein relativedisposition of the coaxial piston and control element with respect tothe tubular member is re-established.

A further salient feature of the present invention provides novelcontrol valving for the power-operated device, coaxiallv disposed whollywithin the tubular piston member for eflicient and long service life.

Another important feature of my invention is the novel adaptation of thedifferent power cylinder constructions herein disclosed and described toaccommodate either airsuspended or vacuum-suspended normal status of themovable power member in re e sed position.

Another object related to the object immediately precedin is theprovision of optional novel power cvlinder assemblies to accommodateeither a solid type-piston or flexible diaphra m as the movable powermember.

In a more specific sense. the present invention seeks to adapt novelpower-operated mechanism in combination with the standard componentscomprising the conventional master cylinder of present-day hydraulicbraking systems commonly emp oyed on motor vehicles. said mechan smoperating the master cylinder with reduced pedal eifort, therebyenabling pumping or feathering control on long downgrades to preventdangerous brake fade due to heat, and in the event of power failure orinadequacy, the master cylinder may be operated directly by the footthrough the pedal in the usual manner and with the usual effort requiredas is understood.

With these and other objects and advantages in view, the inventionconsists of the new and novel combination, construction, and arrangementof parts as hereinafter more fully described, set forth in the claimsappended hereto, and disclosed in the accompanying drawings forming parthereof, wherein:

4 4 Figure 1 is a schematic view of a side elevation of my improvedliquid pressure producing mechanism constructed in accordance with thepresent invention, and shown exemplarily connected diagrammatically tooperate a hydraulic brake system of an automotive vehicle or the like:

Figure 2 is an enlarged longitudnal sectional View, partly in sideelevation, of the brake operating mechanism per se shown in Figure 1wherein the brakes are in fully released condition; 7

Figure 2A is a fragmentary section of Figure 2 on an enlarged scale,showing the novel cup seal and spring seat assembly associated with thepiston head of the master cylinder, for clarity of detail;

Figure 3 is a rear elevation partly in section taken along the line 33of Figure 2 looking in the direction of the arrows, and showing detailsof the portion of the power assembly mounted on the vehicle firewall,and in which is housed the air cleaner;

Figure 4 is a transverse sectional view taken along the line 44 ofFigure 2 looking in the direction of the arrows, and showing details ofthe releasable connection between the movable power member and primarytubular piston including the connection to the vacuum source andassociated air-vacuum passageways in the coaxially disposed controlvalve element;

Figure 5 is a transverse sectional view taken along the line 55 ofFigure 2 looking in the direction of the arrows and showing details ofthe annular collar pressfitted on the tubular pressure-transmittingpiston and which carries the vacuum-air passageways communicating withthe vacuum power chamber;

Figure 6 is a modified form of the invention in which the movable powerassembly is normally vacuum-suspended in released position;

Figure 7 is another modified form of the invention in which the movablepower assembly comprises a solid piston in lieu of the flexible powerdiaphragm;

Figure 8 is another modified form of the invention showing a differentmounting of the annular ring-type cup seal on the head end of thetubular piston which includes a modified star-shaped reed valve toreplace the ring valve of the Figure 1 embodiment;

Figure 9 is a transverse sectional view of the Figure 8 modificationtaken along the line 9--9 thereof;

Figure 10 is another modified form of the invention in which thereleasable connection between the movable power member and tubularpiston is eliminated by making the member rigid with the piston formovement in unison;

Figure 11 illustrates another modified form of the invention forcontrolling the by-pass or compensating port normally open between themaster cylinder pressure chamber and reservoir and for sealing off thepressure chamber from the two hydraulic pistons projectable into saidchamber; and

Figure 12 illustrates another modified form of the invention foranchoring the peripheral marginal portion of the flexible powerdiaphragm in air-tight sealed relation with respect to the interior of amodified form of the power cylinder.

Referring now to the drawings, and particularly Figures l, 2 and 2A, myimproved hydraulic pressure producing device generally indicated at Acomprises a power cylinder B and a hydraulic master cylinder C having anintergal end flange 8 for preferably mounting it on one end of the powercylinder as by cap bolts 1'9 threaded into a plate 11 secured as byrivets 12 to the cylinder end. The end of the hydraulic cylinder remotefrom the power cylinder has a discharge port 14 which is connected byone or more conduits 15 to one or more hydraulically actuated motors orwheel cylinders 16, which may be employed to operate automotive wheelbrakes generally designated D."

The interior of the hydraulic cylinder C is formed as a pressure workingchamber 18, wherein the operating pressure for the wheel cylinders 16 isdeveloped jointly by the force exerted by a power assembly generallyindicated at E movable within the power cylinder B and the force exertedby the operator on a pedal 2d. The

upper end of the pedal, for example, is pivotally supported at 21 .on abracket 22 secured by bolts 23 between the firewall 24 and dash panel(not shown) in the operators compartment of the vehicle. At a pointbelow the pivot 21 the pedal is pivotally connected by means of a pin 25to a clevis 26 formed on one end of a thrust or push rod 27 to provide,for example, a 5 to 1 leverage ratio between the thrust connectionaforesaid and a foot pad 28 at the lower end of the pedal.

The power cylinder B is preferably a differential air pressure operatedcylinder, utilizing either vacuum or compressed air to provide thenecessary pressure diiferential across the movable power assemblyaforesaid. vIn ordinary automotive installations, a vacuum-operatedpower cylinder is preferable to a compressed air operated powercylinder, since the conventional engine intakernanifold, such as shownfragmentarily at 30 in Figure 1, may serve as the vacuum source withoutaffecting engine performance.

The vacuum power cylinder in the preferred illustrated embodiment of theinvention (Figure l) is atmospheresuspended; i.e., air at atmosphericpressure is normally .on both sides of the movable power assembly Ewhich may take the form of a flexible diaphragm or rigid piston, whenthe mechanism is in released position best demonstrated in Figures 2 and2A. Although a vacuumsuspended power cylinder herein illustrated as amodified form of the invention may be used if desired, there are certainadvantages accruing from the use of an atmosphere-suspendedpowercylinder as, for example, chamber 31 of the power cylinder does nothaveto be sealed, since it is maintained under atrnospheric pressure. Thatis to say, the angular movement of control rod 27 during the pressurestroke does not create any structural problem in the design of the powercylinder. Moreover, operation of an atmosphere-suspended power member isinherently smoother and less sensitive than the operation of avacuum-suspended power member. On the other hand, speed of operation,which is the primary advantage of the vacuum-suspended arrangement, isnot considered vital in installations where my improved pressureproducing device would most likely be used as against installations inheavy-duty installations. Actually a slowed more controlled build-up ofpower force during initial stages of vehicular brake application isconducive to preventing sudden stops particularly those stops during lowvehicular speeds as when cruising in congested traflic-light controlledintersections, etc.

The movable power assembly E, which is referred to in certain of theclaims as a pressure-responsive movable wall or member, forms with theinside of the end wall 32 on which the hydraulic cylinder Cis mounted, acon trol or vacuum power chamber 33 within the power cylinder B. Anormally preloaded helically formed return spring 35, usually inpractice of conical configuration, is operably disposed in the powerchamber between the inside of the end wall 32 and confronting side ofthe movable power assembly E for biasing the latter toward releasedposition.

A central annular opening 37 formed with an inturned flange 38 isprovided in the end wall aforesaid, into which an annular hub portion ofthe master cylinder projects in air-tight sealing relationship as by theillustrated pliant O-ring seal 39 carried in the annular channelformerly utilized for anchoring the forward end of a dust excludingmember such as a flexible boot, to prevent escape of vacuum from thepower chamber 33. An axially bored pressure-transmitting or workingmember designated as a whole 49 operably projects through said hubportion in coaxial relation thereto, said member will be referred to in,certain of the claims as a hydraulic pis ton .or plunger, or a primarypiston or plunger for flexibility in terminology, and is adapted tooperably project in fluid-tight sealed relation into the working orpressure producing chamber 18 of the hydraulic cylinder. The powercylinder B is formed of two cylindrical cup-shaped members 42 and 43having their cylindrical wall portions of their open ends telescoped. Amarginal edge portion 45 of the inner member 43 is formed with .anexternal annular channel 46 adapted to receivean annular bead 43 on aflexible diaphragm 49 preferably made of molded rubber, said channelbeing effective in assembled relationship with respect to the innercylindrical surface of the outer member 42 to slightly deform the beadunder compression and thus secure the peripheral edge of the diaphragmin airtight operating condition within the power cylinder.

A plurality-of cap bolts 51 are threaded from the exterior through theoverlapping cylindrical walls of the two members 42 and 43 rearwardlyadjacent the channel 46 to secure the twomembers rigidly assembled asshown in Figure 2. The diaphragm 49 has a central opening 52 with itsedge portion formed with a double annular head 53 which is clampedbetween confronting annular channels 54 and 55 formed respectively in anannular end flange 57 integral with a sleeve 58 and a detachableclamping plate 59 secured to the flange 57 as by cap bolts 60, thediaphragm, flange, sleeve, and clamping plate to thus form in assembledrelation the movable power assembly E.

The portion of the'axially bored working member lii projecting into theworking chamberltl comprises a spool type assembly having an annularhead land 62, an annular shoulder 63 longitudinally spaced from the headland to provide an annular liquid space 64 therebetween and which .isadapted-to have uninterrupted communication via an intake .port 66leading .to a liquid reservoir F associated with the hydraulic mastercylinder C. Adjacentthe shoulder63is anannular groove or channel 68 forreception of an annular single lip seal 69 preferably made offlexiblerubber. The end .face of the head land 62 is equipped with an annularpliant cup seal 32% having a plurality of .circumferentially spacedflutes 72 in the outer surface of its periphery. The central portion ofthe cup is formed with a forwardly extending hollow dome-shapedembossment 321 which is coaxially disposed with respect to a reactivepiston or plunger 322 having a complemental dome-shaped end projectingforwardly of the face of thehead land .62 in coaxial disposition withrespect to said spool-type assembly into contact with the inner surfaceof the embossment, said reactive piston being also termed a secondarypiston or plunger for flexibility in terminology. A vertical web or wall323 interconnects the embossment with a peripheral lip portion 324 ofthe seal and is adaptel to engage the end face of the piston head 62with the peripheral heel portion of the lip indented as at 81 to receivea Washer-type valve ring 82 bonded to the cup to control a plurality ofliquid passageways 83 which accommodate flow of liquid via flutes 72between the annular space 64 and working chamber 18. A movable springseat 325 having a central dome-shaped extrusion to seat against theexterior of the cup embossment 321, is formed with inner and outer legsor flanges 326 and 327, respectively, which are interconnected by avertical web portion 328 with a central opening 329 provided in theflange 326, the web portion normally bearing against or closely adjacentto the cup wall 323 under influence of a reactive and return springoperably disposed in the Working chamber 11:? which will be fullydescribed hereinafter, thus providing means for maintaining the cup sealin substantially juxtaposed relation with respect to the head land 62during the working stroke thereof to displace liquid under pressurethrough the discharge port 14 and to assist in the return of the primarypiston 40 to released position, said 7 V spring also serving theimportant function of continuous reaction on the dome-end of the coaxialpiston 322 via the spring seat and cup dome portions to providesupplemental reactive force on the pedal 20 according to the operatingstroke of both pistons 40, 322 whereby said spring reacts only on thepedal via said plunger 322 during brake-applying operations and on bothof said pistons during brake-releasing operations to establish them intheir respective released positions. A removable valve seat 91 encirclesthe discharge port 14 and is adapted to engage the end wall 92 of thepressure working chamber 18. A residual pressure check-valve assembly Ghaving an outturned annular flange 93 movably engages the seat 91, saidcheck-valve assembly having a self-contained pressure discharge one-waycheckvalve 95 for enabling liquid under pressure to be displaced throughthe discharge port 14, and which cooperates with a seat 96 encircling anopening 97 through the end wall of the check-valve G casing 98 under theinfluence of a normally preloaled compression spring 101.

The previously mentioned reactive and return compression springdesignated by the reference numeral 103 is preferably of conicalconfiguration and operably dis posed in the working chamber 18 betweenthe spring seat 325 and flange 93 whereby its biasing action controlsseating of the check-valve assembly G and continuously reacts on thespring seat 325 and secondary piston 322, thus spring 103 may be termeda valve control and reactive spring for novel purposes which will bemore fullv appreciated in the course of the description to follow. W thfurther reference to the spring 103 it is desired to point out that thisspring is characterized by increasing tension above a pre-energizedstatus, progressively induced by operating the pedal 20 from releasedposition, and since its other function is to control the residualpressure check-valve G, the preloaded normally installed status of thisspring cannot exceed the tension required to maintain substantially -10psi. in the hydraulic lines external to the discharge port 14 inaccordance with factory specification. However, if this spring is notemployed to control the residual pressure checkvalve, as would be thecase where a self-contained residual checkvalve is used, then thepreloaded tension of this spring may be selectively set to whateverinitial reaction on the pedal is desired as its reaction in no wayopposes a brakeapplying movement of the power assembly E. Therefore, nopower loss can result from the power member E having to overcome notonly the reaction from its own re (1131; spring 35 but also the addedreaction from spring The tubular working member 40 also includes anaxial bore 105 coaxiallv merging with a counterbore 106 of largerdiameter leading to the outer terminus of the tubular member, and areduced diameter bore 330 substantially in circular alignment with thehead land 62 and through which the dome-end of the reactive plunger 322projects into contact with the embossment on the cup 320. This reduceddiameter bore forms an internal annular shoulder 331 with the bore 105,the latter bore being longitudinally spaced forwardly from an annularland 332 formed on the plunger 322 to provide an annular liquid space333 therebetween, said land having a working fit with respect to thebore 105 and carries a ring-type pliant seal 117 in an annular channel118 formed medially therein. A port 114 through the wall separating theannular spaces 64 and 333 maintains liquid communication between thesespaces. Accordingly, the aforesaid seals cooperate to confine all staticliquid within the reservoir F and the two annular spaces aforesaid.

A slide valve element 128 is disposed in the counterbore 106 of thetubular member 40 for controlling operation of the power assembly E.This valve is the spool-type and comprises two longitudinally spacedannular lands 129 and 130 forming an annular vacuum space 131therebetween, a closed end axial bore 132 which is intersected by crossbore 133 through the wall of the valve, and a counterbore 134 mergingwith the bore 132 and extending to the outer terminus of the valveelement. A split retainer ring 135 engages an annular groove 136 in theinner surface of the counterbore 106 adjacent the outer terminus of thetubular member 40 to establish the valve element 128 and associatedparts in their normal released positions best shown in Figure 2. Areduced extension 137 terminates the inner end of the valve element 128through which the cross bores 133 are made, and is adapted to normallyengage the confronting end of the reactive plunger stem 121 whereby thecompression spring 103 is normally effective to bias the reactiveplunger 322 and valve element 128 to their respective released positionsas shown in Figure 2. An internal annular shoulder 139 is formed at thepoint of mergence between the longitudinal bore 105 and counterbore 106,said shoulder being engaged by a thrust washer 140 having a centralopening 141 through which the inner end of the stem 121 operablyprojects into engagement with the confronting end of the reducedextension 137. A predetermined lost-motion space 142 is defined betweenthe washer 140 and confronting end of the reduced extension 137 forlimiting relative movement of the reactive piston 322 and slide valve128 with respect to the tubular member 40, and a normally preloadedthrust-transmitting compression spring 144 is operably disposed betweenthe washer and a shoulder 145 formed by the mergence of the reducedextension 137 with the inner annular land 129 on the slide valve 128 toreturn the latter to its normally released closed position shown inFigure 2 in cooperation with the spring 103.

The merging point of the counterbore 134 with the axial bore 132 of theslide valve element 128 provides an internal annular shoulder 147against which the free end of the push rod 27 acts to enable operatorforce applied on the pedal 20 to actuate the slide valve element andreactive plunger in opposition to the biasing force of the two springs103 and 144 and the proportional liquid pressure condition within theworking chamber 18 whereby the operator is given a reduced feel of thedegree of total brake applying force effective at the wheel cylinders16.

An atmospheric chamber 149 is formed in the interior of the tubularmember 40 between the washer 140 and inner annular land 129 and which isconnected to atmosphere via the cross bores 133, axial bore 132 andcounterbore 134. A port 151 is provided in the tubular member 40normally communicating with the atmospheric chamber 31 when the slidevalve 128 is released as shown in Figure 2. This latter port iscontrollable by the annular valve land 129 to selectively connect theport to vacuum and atmosphere. Another port 152 passes through the wallof the tubular member 40 for communicating at all times with the annularspace 131, and an annular O-ring seal 153 is provided in an annularchannel 154 in the outer valve land 130 to insure against loss of vacuumpast this valve land.

The flange sleeves 57, 58 are formed with an internal annular recessedportion 156 and a reduced annular recess 157 respectively providing anannular shoulder 158 therebetween. A thrust-receiving collar 160 ispressfitted on the outer diameter of the tubular member 40 normally incircular alignment with the recess 156. This collar has a reducedannular shouldered extension 161 on which is press-fitted an annularvalve seat 162 preferably composed of hard rubber or suitable plasticmaterial. The inner face of this valve ring is adapted to normallyengage a complemental confronting circular face on the shoulder 158thereby converting the reduced recess 157 into an annular channel 165encircling the tubular member 40 in air-tight sealed relationship. Apair of longitudinal passageways 166 in the collar connects the powerchamber 33 and channel 165. This channel is in circular alignmentwith-port151 at all times, and an external flange 168 is p rovidedon'the tubular member 49 to establish the circular a' ignment betweenthe channel 165 and port 151, and also to insure that the collar 160cannot be axially displaced from its operating position on toe tubularmember should the press-fit connection become inadequate. A plurality ofcircumferentially spaced recesses 169 are provided in the exteriorsurface of the tubular member 40 substantially-in medially circularalignment with the sleeve portion 58 through which the outer end of thetubular member slidably projects through a bearing support opening 171with an angular outturned marginal edge 172. from the central portion ofthe end wall 173 of the inner cup-shaped member 43 of the powercylinder. A plurality of movable detent elements 175, preferably balls,are disposed in a corresponding number of radial threaded bores 176through the wall of the sleeve 58 in registry with theaforesaidrecesses. A threaded plug 177 provided with a cross slot 173, acentral venting bore 179 and a counterbore 180, is adapted to screw intothe outer ends of each of said bores 176 to close the same, and anormally preloaded compression spring 181 is disposed in each of saidcounterbores in engagement with each of the detent elements aforesaid tobias said elements inwardly into engagement with their cooperatingrecesses. As clearly depicted in Figure 2, the curved surfaces or" thedetent elements are adapted to engage a portion of the side walls of therecesses 169 to induce opposed tension between the sleeve 53 and tubularmember as to eflect sealing between the annular valve seat 162 and fixedvalve seat 153 to insure against lealthy between the annular channel 165and power chamber 33. From the foregoing it isapparent that atmosphericcommunication to the power chamber 33 in normal released statusportrayed in Figure 2 is established in part via longitudinalpassageways 166, annular channel 165, port 151, cross bore 133, axialbore 132, and counterbore 134.

An air filter assembly generally designated H is pro vided between endwall 173 of the inner power cylinder member 43 and a substantiallyrectangular mounting member 183 preferably formed as a sheet metaldishshaped stamping with theedge thereof held in spaced relation to theend wall 173 by spacer sleeves 18 3 encircling mounting bolts 23 bestdemonstrated. in Figures 2 and 3. These mounting bolts, usually four innumber, are anchored in suitable openings 185 in the end wall .of themember 43 and project. through corresponding-openings 186 in thestamping 183 and thence through similar openings in the vehicle firewall24 and bracket .22, which when secured together by the bolts 23se1ve.to'mount my liquid pressure producing device A in operating position ona motor vehicle best shown in Figure l. The air filter assembly Hcomprises inner and outer metallic shells 189 and 1% of circularconfiguration with their vertical walls 191 and 192 respectively securedtogether as by welding to provide an annular space 1% between saidcircular walls. The inner and outer circular Walls are perforated as at196 and respectively, and the annular space is filled with screeningmaterial 199 such as metallic wool. A circular opening 2411 is providedbetween vertical walls 202 and 233, which communicates with holes 204 incircular alignment therewith through the end-wall 173 of the member 13thus placing theatmospheric chamber 31 in communication with the aircleaner perforationswhich in turn are in constant communication with anannular space 206 obtaining between an outturned centrally disposedspaced flange 207 and the tubular member 40, said flange 297 beingprovided with anexternal channel 2% to receive an internal annular band209 on a dust excluding flexible boot 210, the'outer end :of said boothaving a reduced annular bead 211 engaging an external groove 212 in thepush rod 27.whereby lIHOVC- ment of the push rod is accommodated :by theboot when .the pedal is opera-ted. The slide valve counterbore 134 beingin constant communication with the annular space 2% thus also utilizesthe air filter assembly H to prevent foreign agencies from entering thepower chamber 33 via the slide valve 128 and consequent possibleimpairment to the valve operation. An offset vertically disposed fiangedportion 214 projects inwardly from the vertical wall portion 191 of theinner air filter shell 189 and has an annular opening 215 therethroughencircling the tubular member 40 in spaced relation thereto. An annularpliant seal 216 is disposed between the angular lip 01 the outturnedflange 172 on the member 40 whereby in assembly, the inner marginal facethereof adjacent the opening therethrough is adapted to place tension onthe sealing ring to slightly deform the same and thus insure a slidingair-tight fit of the tubular member 40 in its bearing support 171.

The sleeve and flange 57, 58 additionally have a longitudinal passageway218 connecting the valve 162 with a port 217 which in turn communicateswith the port 152 in the tubular member 40, said passageway 218 beingclosed by the collar when engaged with the shoulder 158 and open whenthe tubular member 40 is moved relatively to the power assembly E, thelatter operation being eflective when operator :force alone is utilizedto operate the tubular member 40 when the power cylinder B cannot beenergized due to fortuitous stoppage of the engine or, as would be thecase in stopping the vehicle after coasting the same before starting theengine.

The sleeve portion 58 also carries an O-ring seal 220 in a correspondinginternal groove 221 adjacent the terminus of the sleeve opposite theflange 57, and which encircles the tubular member 46 to prevent vacuumloss therebetween.

The port 217 is equipped with a rigid tubular fitting 223, and anotherrigid tubular fitting 2243 having a medially attached mounting flange225 is secured to the exterior of the cylindrical wall of the innerpower cylinder member 4-3, with one end 226 of the fitting 224 extendinginto the atmospheric chamber 31 and the other end 227 projecting fromthe exterior of the cylinder. A flexible conduit 228 serves to connect arigid tubular fitting 229 on the intake-manifold 3t) to the outer end227 of the fitting 224. Another section of flexible conduit 230 formingsubstantially a convolution is positioned within the atmospheric chamber31 in encircling relation to the sleeve 58 and serves to connect thefitting 223 with the inner end 226 of the fitting whereby the port 152is connected to the source of vacuum enabling energization of the powerchamber via passageway 218 when the tubular member 4t) is separated fromthe movable power assembly E or via the slide valve 123 when the plungermember 46 and assembly E are nor mally connected together as shown inFigure 2 for con joint movement responsive to relative sliding movementsof the slide valve 128 induced by operation of the pedal 20 as isunderstood.

A restricted relief passageway shown at 231 between the liquid reservoirand pressure working chamber which is standard in all conventionalhydraulic master cylinders of the type illustrated herein, is maintainedclosed throughout the full operating stroke of the tubular mem-- ber 40in a brake-applying direction and opened upon full release of the pedal20 thus retaining the function of this passageway so that in fieldinstallations of my novel pressure-producing device A, the mastercylinder installed at the factory can be used. In this way a lower costunit to the public is provided over competitive powerbrakes whichrequire specially designed master cylinders sold with the power unit asa unitary assembly at an increase in price to the car owner and with nosalvage value in the discarded master cylinder removed from the car.However, the present invention contemplates unitary assemblies of thepower and master cylinders for either factory or field installation.This passageway is 11 efiective to compensate for excessive liquid inthe hydraulic system upon full release of the brakes so that such excesscan be returned to the reservoir F as is well understood in the brakeart.

The free end of the valve push rod 27 has an axial passageway 233 and across passageway 234 intersecting the passageway 233 to accommodate freepassage of air from the counterbore 134 to the valve axial bore 132.This arrangement is by way of example only, since the shoulder 147formed by the mergence of the bores 132, 134 may be engaged by the freeend of the push rod in such manner as not to obstruct free passage ofair through said bores to the power chamber 33 when the brakes are beingreleased. In this connection it is desired to point out that were thepassageways 233, removed from the end of the push rod 27, the brakes maybe released since the pedal 20 moves faster than the withdrawal of thepower member 40. This action would cause the free end of the push rod tobecome disengaged from the shoulder 147 at the inner end of thecounterbore 134 thus enabling air to freely pass by the end of the pushrod into the valve bore 132 and thence into the power chamber 33 viacross bores 133 and port 151 so that the power member B will retracttoward released position shown in Figure 2. Accordingly, with thespherical end of the push rod devoid of the passageways 233, 234, whenengaged with the shoulder 147 to actuate the slide valve 123 acts as avalve to close the outer end of the valve bore 132 thus supplementingthe valve land 129 to prevent air from entering the power chamber 33 viathe port 151, but when the pedal 20 is released to take the brakes offthe end of the push rod becomes slightly spaced or disengaged from theshoulder 1 -17 to enable air to enter the valve bore 132 whereby thepower member E can return to its released position under influence ofsprings 103, 35 according to pedal movement. In practice, with thedevice A in fully released position, portrayed in Figure 2, theactuating end of the push rod 27 is slightly spaced from the shoulder147to insure complete release of the brakes.

Therefore, the present invention contemplates push rod constructionhaving its valve actuating end with passageways 233, 234-, or devoid ofthese passageways whereby the end of the push rod is so formed as tocooperate with a complemental surface on the shoulder 147 for ventingbore 132 to atmosphere via counter'oore 134 when the rod end disengagesfrom said shoulder.

Operation Assuming that the device A is installed on a motor r vehicleas the present disclosure exemplarily demonstrates in Figure l, tooperate the hydraulic brake system commonly employed on such vehiclesand the device A is in released brake oil condition as depicted inFigures 1, 2 and 2A. With the engine running, reduced pressure (vacuum)is produced within the intake-manifold M which is conveyed throughconduits 223 and 23% via ports 217 and 152 to the vacuum space 131 thussubstantially evacuating the air therefrom. The device is nowconditioned for power operation by depressing the pedal 2t) whichinitially moves the valve element 128 and reactive piston 322 in unisonwith the tubular member 40 against the bias of spring 103, the tubularmember 49 and power assembly B being urged toward their respectivereleased positions by springs 163 and 35. The operator is apprised ofthe degree of braking pressure being developed before and after thepower phase becomes effective by the combined reactive forces producedby the effects of the two springs 11b3, 144 and the hydraulicpressureacting on the end of the reactive piston 322. Initial movement of thepedal 20 moves the reactive piston 322 with the valve element 128 andtubular member 40 relatively to the power piston E accommodated byrelease of the spring-pressed detent elements 175, to close thecompensating port 231 and thus conditions the pressure working chamber18 to displace liquid under pressure via check-valve through thedischarge port 14 into the wheel cylinders 16 to apply the brakes as isunderstood. At the same time the movable power member E is maintained inits released position as shown in Figure 2 due to the aforesaid releaseof the tubular member therefrom responsive to initial depression of thepedal 20. Increase of pressure on the pedal 20 projects both pistons 40,322 further into the working chamber 18 causing a build up of pressuretherein which is transmitted to the wheel cylinder 16 via the dischargeport 14 to bring the brake shoes into substantial frictional contactwith their respective drums wherein all slack is taken up in the system,such increase of pressure build up at this point acting to arrestfurther movement of the tubular member by the pedal and thus overcomesthe preenergized status of the thrust-transmitting spring 144 enablingrelative movement of the control valve 128 and reactive plunger 322 withrespect to the tubular member 40 to cause the valve land 129 on thevalve element 123 to close the port 151 in constant communication withthe power chamber 33 via annular channel 157 and passageways 166 andreaching the relative disposition with respect to the port 151 inreadiness to crack this port as demonstrated by the dashed linedisposition of the parts in Figures 2 and 2A, whereby vacuum enters thepower chamber 33 and thus evacuates the same of air as is understood.This action sets up a differential pressure condition across oppositesides of the movable power member E causing it to move leftwardsubstantially proportional to the extent of movement of the pedal 20into operative thrust-applying engagement with the collar 160 to providepower assistance in a brakeapplying direction.

The resilient characteristic of the cup seal 320 enables the reactiveplunger 322 to move relatively to the primary piston 40, and in so doingslightly elongates the embossment, while the elasticity of the cup sealembossment combined with the reaction of spring 103 via spring seat 325tend to push the reactive piston 322 in opposition to pedal movementthereof. This latter action plus spring 144 provide the operator with anawareness of the efiective braking force supplementally to the pressureacting across the end of the embossment of the cup seal engaging thedome-head of the reactive piston 322. The pliancy of the cup embossment321 enables the spring 103 to react sufficiently close to the web 323 ofthe cup to maintain it and the lip portion in proper sealing relationwith respect to the cylindrical surface of the working chamber 18throughout the full working stroke of the head land 62. During thepressure working movement of the piston 40, the pressure conditionwithin the working chamber supplements the action of spring 103 tostabilize the cup seal against the head of the piston 40 in effectivesealing relationship with respect thereto as clearly depicted in Figures2 and 2A.

It is important to further observe that the magnitude of the reducedhydraulic reaction on the pedal 24 exerted by the pressurized brakefluid on the end of the reactive piston 322 can be varied in accordancewith the diameter of such element. However, this reduced reactive forcewill always be proportional to the force with which the brake shoes arefrictionally applied to the vehicle brake drums, to provide the operatorwith accurate sensing of the amount of braking force being applied. Thisbydraulic reaction principle is in sharp contrast to the controlcharacteristic provided by the spring 103 against which the controlvalve piston 128 is adjusted to control operative energization of thevacuum-motor B since resistance to depression of the pedal 20 increasesin direct proportion to the distance it is depressed rather thanpressure conditions to which the piston 322 is subjected. Therefore,such spring resistance alone would not necessarily have a magnitudecorrelated with the amount of braking force in effect for every positionof the brakepedal, and due to the use of this spring to control theresidual pressure valve G its maximum preloaded status cannot exceed-12# to establish the required residual line pressure, its magnitudewould not be suflicient to provide the necessary reaction. As spring 103is additionally compressed above its normally preloaded status shown inFigure 2, to the position demonstrated by dashed lines in this figure,it provides increasing resistance to pedal movement up to the point ofthe brake fluid becoming initially pressurized under influence ofoperator effort exerted directly on the piston 322 and indirectly on theprimary piston 40 via the spring 144 according to the lattersthrust-transmitting capacity in substantially its preloaded statusdepicted in Figure 2. Thereafter, resistance becomes substantiallyconstant as a consequence of the substantially stationary conditionassumed by the fluiddisplacing parts (pistons 40, 322) resulting fromthe noncompressible column of brake fluid.

Accordingly, the reactive forces from the spring 103 and piston 322 areteamed together with the piston supplying the major portion of thesecombined diminutive reactions as a measure of the amount of brakingforce in effect at any given position of the pedal '20 at which thefluid is pressurized along its full operating stroke while the reactiveforce from the spring becomes substantially constant at the point thefluid reaches such a pressurized state. Spring 103 also combines withthe vacuum-motor diaphragm return spring 35 to return the control valveparts and power diaphragm E to their respective normally releasedpositions shown in Figure 2, yet spring 103 does not interfere withmovement of the power diaphragm E in a pressure-producing directionsince this spring is operated ahead out of engagement with the head land62 in response to operator effort applied to the pedal 20 while themotor B is energized.

Since reaction from spring 103 is effective to a limited extent definedby the control of the residual pressure valve G and the distance thepedal 20 is moved to a point at which the brake fluid becomespressurized under influence of the vacuum-motor B, it serves to bestadvantage as a reaction means by utilizing its yielding resistancethrough substantially the first-half of the series of potentialpressurizing movements along the full operating stroke of the primarypiston 40 which may be had by keeping the brakes properly adjusted andthe system free of leaks which service operations contribute to saferdriving. At pressurizing points beyond the halfway mark aforesaid of thepiston 40, reaction from spring 103 would not sufiiciently resist pedalmovement to prevent power-surge from the motor B resulting from fastidle travel of the pedal in taking up such abnormal slack in the systembefore the motor could be energized to provide power assistance.

The foregoing operation completes what may be termed the applied stage.With the brakes in applied condition, if the operator force on the pedal20 is halted the movable power member B will slightly advance in thebrake-applying direction to produce what may be termed the poised stageat any applied position of the primary piston 40. This latter operatedstage is brought about by a lapped" condition of the annular land 129with respect to the port 151 induced by aforesaid slight relativemovement of the primary piston 40 with respect to the slide valve 128 inthe event brake pedal movement is halted as substantial-1y exemplifiedin Figure 2 showing the relative position of the valve land 129 indashed lines ready to crack the port 151. Thus the brakes may be held onwith minimum operator effort on the pedal as a result of substantialcounterbalance between the differentialpressures aforesaid acting on thepower member E and the existent hydraulic pressure in the hydrauliclines, If the power cylinder should fail to be effective or inadequate,the force exerted by the operator on the pedal 20 will bring the innerend of the valve extension 137 into engagement with the thrust washer140, enabling the operator to operate the device A with physical forcealone, if necessary, to attain the required displacement of liquid intothe hydraulic system. With the power phase effective, however,incremental depressing and releasing movements of the brake pedal 20cause corresponding follow-up movements substantially of the movablepower member E to apply and release the vehicle brakes in a mannerreplete in the brake art.

During the applying stroke of the primary piston 40, the reactive piston322 is held forwardly relatively to the tubular member which disengagesthe spring seat 325 from the head 62 thus nullifying reaction of spring103 thereagainst, yet liquid pressure reaction plus reaction fromsprings 103, 144 on the reactive piston 322 and the valve element 128respectively, and thence to the pedal 20 via the push rod 27 iseffective at all times when the valve element 128 is open causingenergized movement of the power member 40 in a brake-applying directionthus providing the operator with a feel of the extent of braking forcein effect at all stages of the operating stroke of the plunger 40. Thisfeel is different and improved over that provided by prior art devicesfor the same purpose in that a controlled movement of the reactingmembers is provided Which simulates the feel normally inherent withpedal-operated master cylinders of conventional design. There is'notendency for the power phase to over-brake at any given applied positionof pedal movement which provides the highly desirable feature of smoothstops at low vehicular speeds. At high vehicular speeds dangerousgrabbing or locking of the wheels is prevented thus producing smoothvehicular deceleration with reduced operator effort in accordance withthe pressure applied on the brake pedal.

That portion of the primary piston operably projecting into thehydraulic pressure working chamber 18 being substantially conventionalin construction and operation, enables the operator to pump the brakesto prevent dangerous brake fade whether the power phase is effective ornot. Thus on long downgrades the operation of the brakes may be carriedout in coop eration with the power phase or independently thereof in theusual manner by pumping the pedal to introduce more liquid from thereservoir into the hydraulic system via the ports 83 controlled by thevalve ring 82 and thence past the lip 324 of the seal 320 via theperipheral surface facilitated by the flutes 72 communicating with thevalve ring 81, as needed. During brake applying movements of the primarypiston 40, the pressure developed on the cup seal 3% is transmitted tothe valve ring 81 to firmly seat said ring on the peripheral face of thehead land 62 to thus close the ports '83 preventing escape of the liquidwhile under pressure back into the reservoir F.

When pressure on the pedal 20 is removed, springs 103 and 144 move thevalve member 128 back to the position in which the power chamber 33 isin communication with the atmosphere. As air enters the chamber 33 viathe air filter H, counterbore 134-, bores 233, 234 in the free end ofthe push rod 27, axial bore 132, cross bores 133 and port 151, thepressure differential is reduced, and eventually dissipated, enablingsprings 35 and 103 to return the primary piston 40 and coaxiallydisposed secondary piston 322 to their respective released positions asportrayed in Figures 1 and 2. As previously pointed out, the spring 144acts in cooperation with spring 103 to return the slide valve element128 to released closed position after a brake applying operation hasbeen made.

During the return stroke, a predetermined pressure is retained in thehydraulic lines by means of the conventional residual pressurecheck-valve G. If the pressure in chamber 18 falls below atmosphericpressure during the return stroke, liquid is drawn through ports 83 fromthe reservoir F past the ring valve 82 via flutes 72 across the seal lip324 into the chamber 18 to maintain said chamber filled. When the brakesare fully off or released as shown in Figures 1 and 2, the residualcheck-valve G influenced to seat by the spring 103 will establish theminimum residual pressure in the hydraulic lines, such as, for example 5to p.s.i. and with port 231 open excess liquid in the system returnsthrough said port to the reservoir and vice versa if additional liquidis required to fill the system. Therefore, the port 231 may be termed acompensating port.

If the power phase is disabled for any reason, sufficient pressure onthe pedal 20 causes the coaxial piston assembly 40, 322 and collar 160to separate from the power assembly E whereby the master cylinder C isoperated by physical force alone in the well known conventional manner,'with increased operator effort being required as is understood. Thisnovel separating feature removes the force of the return spring 35 fromthe pedal action, and in the case of a piston-type power assembly,friction between the leather seal and inner surface of the powercylinder offers no resistance to pedal movement, also where the powerpiston or diaphragm is not detachable from the primary piston 40requiring that such power member be moved by operator force on the pedal20, the resistance caused by working the air via the valve element 128into and out of the power chamber 33 is also eliminated. Thus, myimproved brake operating mechanism A may be operated in usual pedalfashion with no additional force required over that normally employed inoperating a conventional hydraulic braking system devoid of powerassistance.

My improved device A is designed primarily for use in brake-actuatinginstallations, such as found on motor vehicles, which are operated by asuspended-type pedal or treadle, rather than the conventional brakepedal extending through the floor of the drivers compartment. Use of thependant-type of pedal as the brake control member simplifies control ofthe brakes since the device A can be readily installed in the enginecompartment on the firewall for accessibility and at the same timeenables movement of the pedal pad 28 which the operators foot engages inaccordance with the mechanical advantage desired. That is to say, if ashortened tr'vel is desired, connection of the push rod 27 isestablished closer to the pedal pad, while if a longer travel withincreased mechanical advantage is desired, the connection aforesaidwould be set closer to the pivot pofnt 21 of the pedal. Where the travelof the pedal is shortened, greater reliance on the power operating phasemust be made since the pedal pad is substantially in alignment with thenormally released position of the adjacent accelerator pedal withconsequent loss of mechanical advantage should the power phase becomedisabled for any reason while operating the brakes, or in applying thebrakes before the engine is started to enable energization of the powercylinder B. The lowpedal pad mounting aforesaid removes some of the timelag incident to the operator transferring his foot from accelerator tobrake pedal and vice versa, and therefore, under certain drivingconditions safety in control of the vehicle may be enhanced. However,actual experience in driving a car equipped with my novelpressure-producing mechanism, dictates that the longer pedal travel isconducive to better power-braking control through the full vehicularspeed range, and added safety is provided should the power phase fail byhaving the increased mechanical leverage advantage instantly availableto operate the brakes in usual pedal fashion without inierference fromthe disabled power device B. Furthermore,

it is difiicult to provide feel control in a brake operating device ofthe type under consideration without definite pedal movement, ratherthan a sensitive pedal travel which tends to cause sudden and erraticoperations of the power device because the operator is deprived of adefinite resisted movement of pedal control prior to the power becomingeffective. It is this later serious disadvantage common in prior artdevices that my improved brake operating device basically seeks toovercome by providing sufiicient movement of the pedal in bringing inthe power phase that sudden stops are avoided, the operator being ableto blend the pedal action with the power phase to produce smooth brakeapplications under all driving conditions of the vehicle irrespective ofthe mode of pedal manipulation.

The aforesaid important advantage is provided in the present inventionthrough the novel combination of a conventional hydraulic mastercylinder associated with a new and novel power device directlycontrollable by an operator-operated pedal. While the prior art isreplete with power-operated master cylinders of conventional or modifiedconstruction which utilize, for example, vacuum or compressed airactuation controlled by either manually or foot-operated valving remotefrom the master cylinder, the present invention places the pedal innovel direct mechanical relation to the parts adapted to control theaction of the power device resulting in pedal control of the power phasesimulating the normal feel when the master cylinder is operated solelyby the pedal but with reduced operator effort being required.

A brief review of the operation of the conventional hydraulic mastercylinder is believed apropos and is set forth below:

The master cylinder performs four essential functions, namely:

(1) Displaces liquid into the system, thus actuating the brake shoesinto contact with the wheel drums.

(2) Develops the liquid pressure necessary for braking, when all shoesare in drum contact.

(3) Compensates for temperature changes or liquid seepage, thusmaintaining the correct volume of liquid in the system.

(4) Charges the system with liquid upon each release of the brakes.

The reservoir F and pressure working cylinder 18 are joined by intakeand by-pass ports. A passage in the reservoir filler cap vents theliquid supply to atmosphere. The intake port is connected via passagesin the head land of the piston to the pressure working chamber, saidpassages being conventionally controlled by a starshaped reed valve, oneleg for each passage, interposed between the primary cup seal and pistonhead face. 7,

With the brakes off, the piston is fully retracted as in Figure l, theresidual pressure check-valve at the outlet or discharge port of thepressure cylinder is closed, and the by-pass port and cylinder intakeport, connecting the cylinder with liquid supply, areopen to enableliquid passage through the by-pass port to compensate the system forchanges in liquid volume; i.e., expansion or contraction due totemperature changes or leakage.

When the brakes are applied, the pedal is depressed to force the pistonand primary cup toward the outlet end of the pressure working cylinder.Initial movement of piston and cup instantly forces liquid through thedischarge port since the by-pass port was closed when the pedal wasinitially depressed. With the by-pass port sealed off the pressureworking stroke begins. Pressure acting on the cup lip assists the cup toseal against a pressure leak past the piston. Pressure opens theresidual pressure check-valve through which liquid is displaced into thehydraulic system and, after brake shoes contact with their respectivewheel drums, hydraulic pressures develop in accordance with the degreeof braking effect desired.

During brake release, the pedal returns to ofi position along with thepiston influenced by return spring action both in the master cylinderand wheel cylinders. Returning liquid retracts the residual check-valveas a unit from its seat, flowing around the valve to enfer the pressureworking cylinder. As the piston returns faster than this liquid canflow, a temporary vacuum is created in the pressure cylinder. Thisvacuum condition causes reserve liquid to enter the pressure cylinderth:ough the intake port and passages in the piston head face and thencepast the relaxed reed valve into the peripheral flutes on the lipportion of the seal. Thfs additional liquid movement collapses theprimary cup lip, flowing around it to help reduce the vacuum andsupercharge the sealed system. As liquid continues to return from theWheel cylinders, the surplus returns to the reservoir through the openby-pass port. Where the cylinder has an open end, a secondary cup on thepiston rear bearing surface prevents leaks from the reservoir.

The residual pressure check-valve has two functions, namely:

(1) To maintain 6-12 p.s.i. hydraulic pressure in the system while thebrakes are released, thus lessening the possibility of atmosphericleakage.

(2) To assist bleeding gases from the system by preventing the entranceof air during the bleeding operation.

The present invention contemplates that the residual pressurecheck-valve may be located in the power unit, or conventionally at theoutlet end of the pressure working chamber or in a branch thereof.

Modified power cylinder and operation In the modified embodimentdepicted in Figure 6, wherein parts analogous to those already describedare designated by like reference characters distinguished, however, bythe addition of the letter a to each numeral and the exponent 1 to eachletter, only closely associated structure of the brake system is shown,and it may be assumed that otherwise the components correspond to thoseof the embodiment first disclosed (Figures l-5).

The power cylinder B is provided with two vacuum chambers 33a and 238,the latter chamber being sealed from the atmosphere by end wall 240 ofmember 43a devoid of the air holes 204.

An air-vacuum control valve 241 is provided with longitudinally spacedannular lands 129a, 242, and 130a forming annular spacs 243 and 244therebetween. Passageway 217a is provided in the sleeve member 58a byremoval of the tube 223 and which communicates continuously with thechamber 238. The land 129a being at all times disposed to the left ofport 151a so that the vacuum condition within chamber 33a is constantlyconnected to the annular space 243 which in turn is normally connectedto the port 152a with the parts in released position as shown in thisview, thereby evacuating both chambers of air. The land 242 isoperatively associated with the port 152a to selectively control thesame for admission of air and vacuum therethrough via passageway 217a tothe chamber 238. Annular passageway 244 is disposed between the land 242and annular land 130a longitudinally spaced therefrom. A radial port 246is provided in the valve element 241 for establishing constantcommunication between the annular passageway 243 and counterbore 134a.

The source of vacuum 30 is connected directly to the interior of thechamber 33a by means of a rigid tubular fitting 247 secured to the powercylinder end wall 32a and a flexible air hose 248, connected to therigid tubular fitting 229 attached to the intake-manifold 30. A collar249 is provided devoid of the valve function described in connectionwith the first embodiment to form the annular channel 165a. This collarreplaces collar 160 since shoulder 161 and valve seat ring 162 are notrequired in this modification.

In operation, this modified structure is controlled by the alreadydescribed pedal movements to slide the valve element 241 relatively tothe primary tubular piston 400, the initial movement of the valve movesthe valve land 242 to a position in which the annular vacuum space 243is isolated from the port 152a and connects the chamber 238 with theannular passageway 244 thereby admitting air into chamber 238 viacounterbore 134a causing a pressure differential to be set up acrossopposite sides of the movable power member E since the chamber 33a isconstantly subjected to vacuum. Accordingly, as the pressure rises inchamber 238, the power member moves leftward to actuate the tubularmember 40a to displace liquid under pressure from the working chamber 18through discharge port 14 into the hydraulic lines and thence into thehydraulic motors 16 to operate the same for the purpose intended.Otherwise, the operation of this modified mechanism is identical to thatof the first disclosure, and therefore, further description is deemedunnecessary.

Modified movable power assembly and operation In the modification shownin Figure 7 parts analogous to those already described are designated bylike reference characters distinguished, however, by the addition of theletter b to each numeral and the exponent 2" to each letter, and thearrangement is essentially similar to that of the two previouslydescribed embodiments, except that a piston-type movable power assemblyE is employed in lieu of the flexible-diaphragm, said assemblycomprising an annular sealing member 250 of L-shaped cross section withthe annular radial leg impinged between peripheral face portions of apair of confronting clamping plates 251 and 252, and an inner disposedplate 253 having a peripheral annular flange 254 adapted to receive anannular oil wick 255 radially biased into contact with the other leg ofthe sealing member by an annular wave type flat spring 256. The clampingmembers having central openings with their marginal portions secured asby the illustrated cap screws 257 to form a unitary assembly with aflange 258, threaded into corresponding circumferentially spaced holesin the medial portion of the latter.

In operation, this modified power assembly functions in the same manneras the flexible diaphragm previously described to actuate the primarytubular piston 40b to displace liquid under pressure from the workingchamber 18 through the discharge port 14b into the wheel cylinders 16for the purpose intended.

Modified master cylinder piston assembly and operation Figures 8 and 9show a modified form of my invention in which corresponding parts aredesignated by like reference characters distinguished, however, by theaddition of the letter c to each numeral and the exponent 3 to eachletter.

The construction of this modification differs primarily from the firstembodiment (Figures l5) in the type of seal associated with the headland 62 of the tubular pressure-transmitting member 40 and the reactivepiston 322 carried thereby.

The end face of the head land 62c is equipped with a ringtyp-e lip seal710 preferably composed of molded rubber having a plurality ofcircumferentially spaced flutes 72c in its peripheral lip surface and acentral annular opening 730. A star-shaped reed valve element 260 isemployed in lieu of the ring valve 82 illustrated in Figures l-5, tocontrol the ports 83c, said reed valve element having an inner annularweb segment 261 integral with a plurality of radially projecting legs262, one for each of the ports 830. This web portion has a centralcircular opening 263 of slightly less diameter than the opening 730 inthe seal 71c to enable the marginal edge por tion of the opening 263 tobe impinged between the face of an external annular shoulder 264provided on a bush ing 265 pressfitted into a counterbore at 79c, andthe marginal confronting face portion on the head of the pri mary piston land 620. An end annularflange 266 is provided on the exterior ofthe bushing 265 and longitudinallyspaced from the web segment 261 toprovide an annular channel 267 for the reception of the marginal portionofthe central opening 73c of the seal 710. The reed valve 260 is mountedbetween the vertical wall of the seal 71c and face of the head land 62cin close adjacency thereto, and the opposite side of the vertical wallof the seal is stabilized against the head land by an annular flangemember 268 secured in coaxial position by a split retainer ring 269engaging an annular groove 270 pro- :vided in the periphery of the endflange 266, said flange member 268 being provided with a series of holes271 therethrough to accommodate free flow of liquid between'opopsitesides thereof.

The bushing 265 has an axial bore 85c through which astemportion 86cslidably projects, said stem portion terminating atits forward end intoa cup-shaped spring seat 870 which replaces seat 325 and normallyengages the flanged end of the bushing, 265. The stem 860 is providedwith a longitudinal bore 88c closed at its inner end "and a plurality oftransverse bores 89c intersecting the longitudinal bore 88c to provideliquid communication between the pressure chamber 180 and theinterior ofthe tubular member 40c leading from the inner end of the bushing 265. Areactive plunger or piston 1080 is slidably disposed in the longitudinal1050 and comprises: an annular head land 1090 having a reduced diameterintegral portion terminating in an annular flange to provide an annularchannel 1110 for reception of the inner marginal portion of a ring-typelip seal 112e, the flanged end of channel 1110 is engaged at all timesby the inner end of the stem portion 86c which carries on its forwardend the said spring seat 870. An annular liquid space 1130 is providedon the piston 1080 between the headland 109's and the land 332e, saidlatter spacecommunicating at all times via the port 1140 through thewall of the tubular member 400 with the annular space 64c and reservoir-F The annular land 332c is provided with the previously disclosed O-ringseal 117a disposed in the ann'ular channel 118a to prevent liquid fromreaching the power chamber 33 via the longitudinal bore 105c.Accordingly, the seals 71c, 109a and 117a cooperate to confine allstatic liquid within the reservoir F and the two annular spacesaforesaid.

In operation, the forward edge of the lip of the seal 710 is normallydisposed to the right of the compensating port 231c to accommodateliquid compensation between the working chamber 180 and reservoir F inthe same manner as described in connection with the first embodiment(Figures 1-5). Initial depression of the pedal moves the slide valve128e, reactive piston ItlScand spring seat'87c in unison with thetubular member 400 to close the compensating port 231c in opposition toprogressive increasing tension of the reactive spring 103a untilpressure conditions within the working chamber 180 arrest further unisonmovement of the tubular member 400; whereupon, the spring 144 yields toaccommodate relative movement of the valve element 128, reactive piston1080 and spring seat 870 to place the valve land 129 in position to openport 151 (see dashed line position of land in Figure 2) therebyenergizing the power member E to produce power assistance in applyingthe brakes in response to increasing pressure on the pedal 20 to thedegree of braking effect desired.

Accordingly, initial movement of the tubular member 400 conditions thepressure working chamber 180 for operation in the same manner asdescribed in connection with the first embodiment (Figures l-5). Allother phases of relative operations of the tubular member 400 withrespect to the power member E are identical to those already describedas-well as the relative movement of the valve element 128, reactivepiston 108a and spring seat 870 in unison with respect to the tubularmember 400, the latter relative movement being accommodated by theyielding of the thrust-transmitting spring 144 after- -the slack in thesystem has been taken up responsive to initial pedal movement. It isthus seen that the present'modification diflers essentially from thefirst embodiment (Figures 1-5) in the replacing of the dome-ended piston322 with the stem mounted spring seat 87c and reactive piston 108c whichrequires modification of the vertical wall of the cup-shaped seal 320 bycentrally aperturing the same for the-stem portion 86c of the springseat 870 to operably project through the bushing 265 while the latter inturn secures the star-shaped reed valve 260 in operating position on theface of the head land 62c andalso provides the exterior channel 267 inwhich the inner marginal portion of the seal 71c is anchored inliquid-tight sealed relation on the head land aforesaid. Otherwise, thenovel functional advantages are substantially similar to those providedin the embodiment depicted in Figures 1-5.

Modified movable power assembly and operation This'modification shown inFigure l0'is also designated by like reference characters previouslyused to identify corresponding parts distinguished, however, by theaddition, of the letter e. to each numeral and the exponent 5 to eachletter, and provides for, the elimination of the releasable connection169, 175 depicted in Figure 1 embodiment, by fixing the power membersleeve 290 directly to the tubular piston member 4%, as by headed pin291 pressfitted into aligned openings 292 and 293, for movementtherewith at' all times. This arrangement also provides for theelimination of the collar andassociated elements together with thelongitudinal passageway 218.

In operation, the power assembly E moves in unison at all times with thetubular member 40e whether this member is-operated by power and/ orphysical force, such being found comme cially practicable wherediaphragmtype of power assembly is employed since only the bias of thereturn spring 35:: must be overcome, but in the case of the piston-typepower assembly, added friction between piston and inner surface of thepower. cylinder, particularly in cold weather operation, builds upagainst pedal effort, and thus the novel separating featurehereinbeforefully described is used to provide lighter pedal movement where thepower phase is disabled Modified primary piston head seal and operationThis modification is depicted in Figure 11 and the arrangement isessentially similar to the Figure 8 embodiment with corresponding partsidentified by' like reference. characters to those previously used'distinguished, however, by'the addition of the letter g't0 each numeraland the exponent 7 to each letter. The construction of this modificationof the invention differs primarily from the Figure 8 embodiment in thetype of sealemployedlon thehead land 62g of the tubularpressure-transmitting member'tlg. The-end face of the head land 62g isequipped with an annular single lip seal 71g composed of molded rubberhaving a plurality of circumferentially spaced flutes 72g in itsperipheral lip surface and a central circular opening 73g having themarginal portion of its outer end formed as a beaded edge 74g normallyunder slight compression by engagement of the confronting surface of anexternal annular flange 76g provided on the end of a sleeve 77gprojecting through said central opening, said sleeve being adapted tohave either limited relative sliding movement or fixed with respect to atubular bushing 78g pressfitted into the counterbore 79g flush with theface of the head land 62g to form the inner terminus of the tubularmemberitig, the heel portion of said seal 71g is provided with acircular peripheral offset portion 81g confronting the face of the headland and adapted to control liquid flow via an annular valve ring 82gcarried on said offset portion and circumferentially spaced longitudinalports 83g through the head land, fromthe annular space 64g into thepressure working chamber 18g. The sleeve 77g has the aforesaid axialbore 85g through which the stem portion 86g of said integrally flangedspring seat 87g slidably projects, said seat as in Figure 8 normallyengaging the flanged end of the sleeve 77g, the stem portion having thelongitudinal bore 38g closed at its inner end and the plurality oftransverse bores 89g intersecting the longitudinal bore 88g to provideliquid communication between the pressure working chamber 18g and theinterior of the tubular member 40g leading from the inner ends of thebushing 78g and sleeve 77g. The reactive plunger or piston lllfig ismovably disposed in the longitudinal bore 105g and comprises the annularhead land 109g having the annular channel 111g for reception of theannular pliant seal 112g, the end wall of channel 111g being engagedwith the inner end of the stem portion 86g which carries the spring seatflange 87g. An annular liquid space 113g is provided on the element 108grearwardly of the head land aforesaid, said space communicating at alltimes via port 114g through the wall of the member 40g connecting theannular space 64g with the interior of the longitudinal bore 105g andthe reservoir F An annular pliant seal 117g is disposed in an annularchannel 118g to prevent the liquid from reaching the power chamber 33gvia the longitudinal bore 105g. Accordingly the seals cooperate toconfine all static liquid within the reservoir F and the two annularspaces aforesaid.

In operation, the lip edge of the cup seal 71 is normally disposed tothe right of the compensating port 231g to accommodate liquidcompensation between the working chamber 18g and reservoir F in the samemanner as described in connection with the previous embodiments. Initialdepression of the pedal 20 moves the slide valve 123g, reactive piston108g and spring seat 87g in unison with the tubular member 40g to closethe compensating port 231g in opposition to the progressive increase oftension in the reactive spring 103g until pres sure conditions withinthe working chamber 18g arrest further unison movement of the tubularmember 40g; whereupon, spring 144g yields to accommodate relativelymovement of the valve element 128g, reactive piston 108g and spring seat87g to cause the valve land 129 to open port 151 thereby energizing thepower member E to produce power assistance in applying the brakes inresponse to increasing pressure on the pedal 20 to the degree of brakingeffect desired.

Accordingly, initial movement of the tubular member 40g conditions thepressure working chamber 18g for operation in the same manner asdescribed in connection with the previous embodiments. All other phasesof relative operations of the tubular member 46g with respect to thepower member E are identical to those already described as well as therelative movement of the valve element 128g, reactive piston 103g andspring seat 87g in unison with respect to the tubular member 40g, thelatter being accommodated by the yielding of the thrusttransmittingspring 144g after the slack in the system has been taken up responsiveto initial pedal operation.

It will be noted that the structural difference between the cup 329 ofthe first embodiment and the cup 71g of the present modification isprimarily in the construction of the vertical wa ls. In the former, thiswall is not apertured centrally while the latter is to enable the stern86g of the spring seat 87g to operably project through the bushing 77gwhich secures the inner periphery of the seal 71g in operating positionwith respect to the head land 62g.

Modified power cylinder assembly This modified power cylinderconstruction depicted in Figure 12 is designed to facilitate assembly ofthe flexible power diaphragm without the necessity of having to anchorits peripheral edge within or on the cylinder casing as by a pluralityof securing means such as bolts or rivets customarily used which add toproduction cost.

This modified structure also uses like identifying reference charactersto those previously applied to corresponding parts distinguished,however, by the addition of the letter h to each numeral and theexponent 8 to each letter. As the illustration clearly demonstrates, thepower cylinder comprises two cup-shaped cylindrical casings or members310 nad 311 of the same diameter having their open confronting endsformed with outturned annular flanges 312 and 313, respectively. Thefitting 224 is mounted on the rear member 311 similarly to that alreadydescribed in connection with the Figure 1 embodiment. An annular sleeve314 is formed with an outer annular channel 315 on the inner end and anannular outturned flange 316 on the outer end. The flanges 312 and 313on the cup-shaped members and flange 316 on the sleeve are provided witha plurality of registering holes 317 (six for example) incircumferentially equally spaced relation, the sleeve flange beingadapted to be clamped between the flanges of the cupshaped members toprovide a unitary assembly.

To assemble this modified power cylinder, the peripheral bead 4811 onthe diaphragm 4911 is inserted in the sleeve channel following which thesleeve is pressed into the position shown wherein its flange contactsthe flange of the forward cup-shaped member. This operation placesradial tension on the annular bead of the diaphragm to slightly deformthe same to effect an air-tight seal with respect to the inner surfaceof the forward cup-shaped member 310 thus forming the power chamber. Theother cup-shaped casing is now placed in position with its flangecontacting the opposite side of the sleeve flange and the bolt holesaforesaid in registry, thereupon bolts 318 are inserted in the holes andtightened to make the power cylinder into a rigid unitary assembly as isunderstood. Thus, assembly or disassembly of the power cylinder may bereadily eflected by clamping the diaphragm sleeve between the cup-shapedmembers or release of the sleeve, respectively. This construction alsofacilitates alignment of the cylinder members with respect to each otherand the hydraulic cylinder mounted on the forward end of one of themembers to prevent binding of the hydraulic primary piston 40 in theassembled device A Operational summary From the foregoing description,taken in connection with the various illustrations of the differentembodiments of my invention, it will be seen that certain interrelatedcomponents of the liquid pressure-producing mechanism A possess similarfunctional characteristics such that interchangeability is readilyeffected, particularly in connection with the power controlling featuresand type of pressure-transmitting member 40 employed in the mastercylinder working chamber 18 which may take the form of a piston havingthe same cross-sectional area as the chamber, or a plunger of lesscross-sectional area than the chamber which, in the latter case, wouldeliminate machining the interior of the chamber but a longer workingstroke would be required. For example, the flexible power diaphragm 49and the piston-type power member 13 may be controlled with substantiallyequal etficiency by either of slide valve elements 128 or 128a, whetherpower cylinder B or B is employed. Either of the power cylinders B or Bis adaptable for actuation by either compressed air or vacuum, and thepedal control of these cylinders may be had with the illustratedpendulum-type pedal 2% or other types such as those commonly on thefloorboard of the drivers compartment. Spring 103 when not employed tocontrol the residual pressure check-valve G, may be made of suchstrength that it alone can return the movable power assembly E toreleased position thus eliminating return spring 35, particularly in thecase where the power member is fixed to the hydraulic piston or plungeras exemplified in Figure 10. Also the ring '23 compensating'valve 82.may be substitutedfor the modifiecL stat-shaped valve 260 of Figures8and.9;

Moreover, several novel combinations are optionally providedby theinterchangeability of the diiferent hydraulic cylinder constructionsherein disclosed which may be. actuated by either the illustratedflexible power diaphragm or powerpiston whether these power membersare:detachable from or rigidly secured to the primary hydraulic piston,the latter being preferably formed of asingle tubular member, while anyof the illustrated variations of the pedal-controlled secondary pistonor plunger coaxially disposed within the hollow of the tubular membermay be readily associated with either of the illustrated variationsin'the primary piston orplunger. Accordingly, a wide range of liquidpressure producing devices A are made available by the present inventionin several different designsto suit individual installationrequirements, that is, whether the unit is for operating the brakes of apleasure car, truck or bus.

Accordingly, the aforesaid components of the present construction afforddiflerent commercially desirable results by providing selective novelcombinations of braking control according to the installation desiredfor the particular type of motor vehicle, that is, whether a commercialor passenger car. Further beneficial results in the braking control of amotor vehicle equipped with my power brake system may be realized in theselective use of the flexible power diaphragm and piston-type powermember since either of these power assemblies is adapted .to notinterfere with normal operator-operation of the hydrauiicmaster cylinderin the event-of complete disablernent of the power or itsinadequacy toprovide the necessary stopping force.

It is important :to point out that the relative strength of spring'144must have a thrust-transmitting capacity in preloaded condition ofgreater magnitude than the combined reaction from spring 103 and thelocking effect of the releasable connecting means 169-175 between theprimary pistonand power member shown in Figures 2 and 4, or the powerassembly return spring 35 where the power member and primary piston forma unitary assembly as demonstrated in Figure 10, to enable the primarypiston to be initially operated against its return spring 63 to closethe compensating port 231 responsive to initial pedal movement thereofto condition the master cylinder C to pressurize the brake fluid priorto operative energization of the power cylinder B under control of theslide valve 123. For example, with the preloaded weight of spring 144greater than the combined installed strength of'spring 103 and theaforesaid locking eifect of the releasable connecting means 169175,resisted by spring 35, or in'the case of the power member E beingsecured to the primary pistondtl for movement therewith greater thanboth of the return springs 35, res, then initial pedal movement in abrake-applying direction would move the primary piston simultaneouslywith the secondary piston 322 and slide valve 123 to close thecompensating port 231 prior to operative energization of the powermember. This latter condition obtains until the reactions from spring 35or 103 or both and pressure in the working chamber of the hydraulicmaster cylinder offer sufficient resistance to overcome spring 144 andthus hold the primary piston 4d from moving forwardly with the secondarypiston 322 and slide valve 128, whereupon the reactive piston 322 andslide valve 128 will move relatively with respect to the tubular piston40 to operate the slide valve 128 into on operating position (see dashedline position of valve land 129 in Figure 2) wherein the vacuum in theengine intake-manifold is connected with the. power chamber 33 of thedevice A. This will cause the power member E to move forwardly and applypressure to the tubular piston 40 in accordance with pedal movement withcorresponding pressure on the liquid in the hydraulic working chambercausing the liquid to be displaced through the discharge port into. the,wheel cylinders to apply the :brakes in awell known manner. As willbeappreciated, such increase in pressure reacts on the-head of thereactive piston 322, thence on the slide valve 128 to the pedaltoprovide the operator with a reactive .force proportionate tototaldisplacement of both pistons.

If, however, the engine is not running, the operator must actuate bothpistons solely by physical force to appy the brakes, and before theworking chamber 18is conditioned to discharge liquid pressure into thehydraulic system, the compensating port 231 must' be closed.

An important feature of braking control results from the use of spring144 which commercial design indicates should be preloaded at 2530 poundsas a thrust-transmitting means between a normal height pedal providingconsiderable mechanical advantage and the primary piston, such that inthe event the brakes are applied initially by a sudden thrust of thepedal, this spring blocks the power-boost application until it can bebrought in to assist pedal operation smoothly and without abrupt shock.This smooth mergence of the power phase with the pedal operation afterthe latter has inaugurated pressure buildup in the master cylinder,avoids power-boost lock of the vehicle wheels with resultant tendency ofthrowing the car occupants forwardly out of their seats, and sometimesleads to loss of control or a potentially dangerous skid. Thus, thepresent invention retains all of the functions of a standard mastercylinder as well as having this important built-in automatic control tooifset the usual effects of too rapid depressing of the brake pedalwhereby the advantages of fully controlled, predictable response areprovided for complete braking safety.

The present invention contemplates use of the so called low-pedal whichplaces the foot pad of the pedal in substantially the same planeoccupied by the accelerator pedal when released, thus enabling aswinging motion of the toe pivoted about the heel from one pedal to theother. This low-pedal arrangement, however, sacrifices considerablemechanical advantage over the master cylinder C making it extremelydiflicult to apply the brakes when vacuum-power is not available as whenthe engine is stopped or a vacuum line breaks. Where a low-pedalconstruction is employed, the suggested 25-30 pound preloaded rating ofthe spring 144 is not required since a spring of this weight would addto pedal load. Therefore, this spring may be reduced in weight to 10-15pounds or even lighter according to the sensitivity of operationdesired. With the lighter spring, the tubular member 40 would not beinitially moved by pedal opera- .tion, but instead, due to yielding ofthis spring, the tubular member would be initially activated by thepower member E to close the compensating port 231. This latter operationresulting from initial relative movement simultaneously of the slidevalve 128 and hydraulic piston 322 with respect to the tubular member 46to open the valve, is provided by the lighter spring 144 yielding inadvance of movement of the tubular member 46 thereby as would be thecase were the spring heavier.

Thus, if a more sensitive pedal feel is desired, the preloaded status ofthe valve spring 144 would be set to substantially counterbalance thatof the master cylinder piston return spring 103 or less than this latterspring. Under such circumstances, the power phase would lead thefoot-operated phase in conditioning the master cylinder C to pressurizethe fluid therein since spring 103 would not yield until the powercylinder B becomes operatively energized but the resistance offered bythis latter spring against the valve spring 144 would not be ofsuflicient magnitude as to prevent a somewhat sudden and erratic initialbuildup of pressure on the brake fluid in the working chamber 18 causingthe wheelbrakes to suddenly apply without sufficient operator awarenessofthe extent of such initial application. If the pretension on thevalvespring 144 isvequal to orlower than that of the master cylinderspring 103, a low-pedal control is recommended to enable control of thepower cylinder B with the foot as distinguished from leg thrust, withconsequent smoother regulation of the initial power phase. It is,therefore, seen that when the valve spring 144 yields in advance of theyielding of the spring 103, that initial actuation of the mastercylinder piston is efiected by the power cylinder B to produce a moresensitized initial brake-applying operation with less operator effortinvolved but requiring a more capacitated booster motor B since morework is required of the latter.

Further considering the novel reactive control operations provided byvarying the size of the opening 329 in the movable spring seat 325, itshould be importantly observed that if the size of this opening isenlarged substantially to the same diameter as the reactive plunger 32.2or even slightly larger, the reaction of the spring 103 on the head endofthe plunger 322 is nullified without sacrificing the force of thisspring as a return agency for the tubular pressure-transmitting member4i) to normally released position. However, the tension, due to thepliancy of the cup embossment 321, continuously reacts on the head ofthe piston 322 in opposition to pedal operation thereof in abrake-applying direction since the vertical wall of the spring seat isin close adjacency thereto the corresponding portion of the cup seal 320during all working positions thereof to maintain this portion inintimate contact with the end face of the tubular member 40. As theplunger 322 and slide valve 128 are moved relatively to the tubularmember 40 by pedal operation from released position to control operativeenergization of the power member E in the manner previously described,the cup embossment 32 1 is slightly elongated due to the pliancy of thematerial with which the cup is constructed to accommodate this relativemovement with the spring 103 reacting on the spring seat to hold the cupvertical wall and lip in normal operating disposition with respect tothe head of the end face land 62. This tension build up in the cupembossment which is a function of the reaction of spring 103 on theother portion of the cup to maintain the latter in sealing position,supplements the reaction of the hydraulic thrust across the head of thepiston 322. If however, the opening 329 is the size illustrated orsmaller, then the marginal overlap of the opening onto the similarportion of the embossment 321 acted on by the plunger 322, enables theplunger to move the spring seat relatively to the head land 62 duringsuch energizing relative movement thereof to add the reaction of thespring 103 to said hydraulic thrust for a more sensitized reactioncontrol and at the same time relieve the biasing etfect of this springfrom the tubular pressure-transmitting member 40 whereby the powermember E operates free of resistance from spring 103 thus providingmaximum power efficiency to apply the hydraulic thrust into the wheelcylinder of the vehicle to operate the brakes as is well understood.From the foregoing, it is clearly demonstrated that the novel adaptationof different size openings 329 in the manner above described results inbeneficial advantages of reaction control to give the operator adefinite and sensitized proportional feel of the total braking force ineffect at incrementally operated positions of the pedal 20 in abrake-applying direction.

With the larger opening 329, the spring 144 alone serves to return theslide valve 128 to its released position with respect to the tubularmember 40, while the smaller opening as illustrated herein enables thecombined forces exerted by springs 103 and 144 to return the reactivemember 322 and slide valve 128 to their respective released positions.In both cases, however, the thrusttransmitting spring 144 acts to resistrelative pedal operation with respect to the tubular member 40 until thepressure buildup in the working chamber 18 has reached such magnitude asto substantially arrest further move- 26 ment of the tubular memberunder influence of the pedal 20.

Considering the terminology used in the foregoing description and in theappended claims, the identifying expressions and/or terms employed areintended to convey meanings which include the range of reasonableequivalents in the patent sense. For example, the expressionsservomotor, power cylinder, power device," power means, power mechanismare intended to include any casing and/or chamber having apressureresponsive movable assembly therein, whether such assemblyincludes a piston, or a flexible diaphragm, or some other member servingthe same purpose. The terms front, rear," right, left, and otherdirectional words or characters are intended to have only relativeconnotation for convenience in describing the structure as illustrated,and are not intended to be interpreted as requiring any particularorientation with respect to associated structure external to the presentdisclosure.

Although it will be apparent that the preferred embodiments of theinvention herein disclosed are well calculated to fulfill the objectsabove stated, it will be appreciated that I do not wish such to belimited to the exact construction and/or arrangement of parts shown,since it is evident that modifications, variations, changes, andsubstitutions may be made therein without departing from the properscope or fair meaning of the subjoined claims.

Having thus described my invention, I claim:

1. In a power-assisted brake operating mechanism wherein there is to beoperated a hydraulic master cylinder having a body member, a hydraulicfluid reservoir and Working chamber in said body member, a compensatingpassageway normally open between said chamber and reservoir, theimprovement which comprises a hydraulic finid-displacing member in saidchamber to pressurize the fluid therein, displacement of which fromnormal released position is opposed by a normally preloaded spring,which master cylinder is adapted to be operator-operated, andpower-assisted by a pressure differential operated servomotor providedwith a casing divided interiorly into a constant pressure chamber and avariable pressure chamber by a power assembly movable therein fromreleased position to act on said hydraulic displacing member, in suchmanner that the initial operator force is transmitted to the hydraulicdisplacing member to close said compensating passageway to condi-- tionthe working chamber of the master cylinder to pres-- surize the brakefluid thereby generating a progressively amplified resistance to suchinitial displacement to induce power-assist by said servomotor; controlvalve mechanism having at least two principal cooperating elementsrelatively displaceable from normal off position wherein said constantand variable chambers are interconnected to establish balanced pressurestherein, and to operating on position wherein said constant and variablechambers are isolated to enable establishment of differential pressurestherein to activate power-assist by said servomotor, said valvemechanism having a fluid connection with said variable pressure chamber;a source of pressure different from atmosphere communicating with saidvalve mechanism; another normally preloaded spring of greater strengththan said first-named spring, reacting between said valve elements toseparate them to normal off position for deactivating power-assist bysaid servomotor, the preloaded strength of said valve spring beingcapable of transmitting said initial operator force until saidresistance induces modulation of the valve spring accompanied by saidrelative displacement of the valve elements to on position to activatepower-assist by said servomotor in response to increased operator force;limiting means in-- corporated between said valve elements to define thenormal off position thereof; reaction means effective on one of saidvalve elements to supplementally oppose said relative displacement ofsaid valve elements against said valve spring; operator-operated meansfor operating said hydraulic displacing member and said valve mechanismincluding a link acting directly on said one valve element to elfectrelative displacement of said valve elements to on position; andnormally spaced engageable portions operatively associated respectivelywith said hydraulic displacing member and one valve element fordefiningthe relative displacement of saidvalve elements, said portionswhen engaged effecting straight-through operation of said hydraulicdisplacing member from said operator-operated link.

2. A brake. operating mechanism constructed in accordance with claim 1including automatically releasable force-transmitting means operablyincorporated between said hydraulic displacing member and said powerassembly to connect them for movement together during powerassistbyrsaid servomotor 3. A brake operating mechanism constructed inaccordance-with claim '2 wherein said force-transmitting means comprise;a normally preloaded spring continu- 'ously reacting between a portionof said servomotor casing and said;power assembly to reset the latter innormal released position; a pair of releasably engageable elements oneof which is spring-loaded, to effect engagement with and accommodatedisengagement from the other. element and disposed respectively on saidpower assembly and the hydraulic displacing member, said elements beingautomatically disengageable to disconnect the hydraulic displacingmember from said power assembly for independent two-directional movementwith respect to the. latter in response to operator force exerted onsaid link in opposition to the preloaded, reaction of said powerassembly resetting spring.

4. A brake operating mechanism constructed in accordance with claim 1wherein said force-transmitting means comprise: an elementinterconnecting said power assembly and hydraulic displacing member in aunitary assembly for conjoint movement.

5. A brake operating mechanism constructed in accordance with claim 1wherein said force-transmitting means comprise: an element fixed on saidhydraulic displacing member, a cooperating element carried by said powerassembly normally engaging said element on the hydraulic displacingmember for movement together in one direction only whereby said powerassembly is capable of acting on said hydraulic displacing member in ahydraulic displacing direction of movement only.

6. A brake operating mechanism constructed in accordance with claim 1wherein-saidreactionmeans comprise: an axial bore in said hydraulicdisplacing member and a hydraulic reaction member slidably disposed insaid bore to receive proportional hydraulic thrust from the pressurizedfluid in said hydraulic working chamber, said reaction member being,adapted to operativelyengage said one valve element for movementtogether when the latter is relatively displaced. with respect to theother valve element under influence of said increasedoperator force onsaid link.

7. In a power-assisted brake operating mechanism wherein thereis to beoperated a hydraulic master cylinder, having a body member, a hydraulicreservoir and working chamber in ,said body member, a compensatingpassageway normally open between said chamber and reservoir, theimprovement which comprises: a hydraulic displacing member in the formvof a longitudinal tubular wall in said chamber to pressurize thefluidtherein, displacement of which from normal released position is opposedby a normally preloaded spring which. master cylinder is adapted to be,operator-operated, and powerassisted by a pressure differential operatedservornotor provided witha casing dividedinteriorly intoa constantpressure chamber and a variable pressure chamber by a power assemblymovable therein from released position to act on said hydraulicdisplacing member, in such man: ner that the initial operator force istransmitted to the hydraulic displacing member to close saidcompensating passageway to. condition the working chamber of the mastercylinder to pressurize the brake fluid thereby generating aprogressively amplified resistance to, such initial displacement toinduce power-assist by said servomotor; control valve mechanism havingat least two principal cooperating elements relatively displaceable fromnormal oil position wherein said constant and variable chambers areinterconnected to establish balanced pressmes therein, and operating toon position wherein said constant and variable chambers are isolated toenable establishment of differential pressures therein to inducepowerassist by said servomotor, one of said valve elements consisting ofa portion of said tubular hydraulic displacing member, and the othervalve element being a piston slidably disposed in said tubular valveportion; a port through the wall of said valve portion; a source ofpressure different from atmosphere communicating with said port; anannular chamber between said valve piston and the tubular valve portionin continuous communication with said port; a second port through theWall of said valve portion interconnecting the interior thereof withsaid variable pressure chamber; a working land on said valve piston forselectively connecting said second port to said annular chamber and tosaid constant pressure chamber; a second normally preloaded spring ofgreater strength than said first-named spring, reacting between saidvalve piston and said tubular valve portion to separate them to normaloff position for de-activating power-assist by said servomotor, thepreloaded strength of said valve spring being capable of transmittingsaid initial operator force until said resistance induces modulation ofthe valve spring accompanied by said relative displacement of the valveelements to on position for activating power-assist by said servomotorin response to increased operator force; limiting means incorporatedbetween said valve portion and said valve piston to define the normaloil. position thereof; reaction means eiiective on the valve piston tosupplements ly oppose relative displacement of the valve elementsagainst said valve spring; automatically releasable force-transmittingmeans operably incorporated between said hydraulic displacing member andpower assembly to connect them for movement together during power-assistby said servo-motor; operator-- operated' means for operating saidhydraulic displacing member and'said valve mechanism including a linkas? ing directly on said valve piston to effect relative displacement ofsaid valve elements to on position; and normally spaced engageableportions operatively associated respectively with'said hydraulicdisplacing member and the valve piston for defining the relativedisplacement-of said valve elements, said portions when engagedeffecting straight-through operation of said hydraulic displacing memberfrom said operator-operated link.

8. A brake operating mechanism constructed in accord ance with claim 7wherein the releasable force-transmitting means comprisea a-sleevemember co-axially fixed to the power assembly through which a portion ofthe hydraulic displacing member projects; a collar fixed on thehydraulic displacing member, one end of which'normally engages the innerconfronting end of the sleeve member; a threaded bore through the wallof the sleeve member, a threaded plug for closing one end of said bore,=an element mo-vably disposed in said bore, a third normally preloadedcompression spring reacting between the plug and movable element, and adepression in the outer face of the hydraulic displacing member forreception of said movable element to releasably connect the sleeve andhydraulic displacing members for unison movement in a power-assistdirection.

9. A brake operating mechanism constructed in accordance with claim 8including a longitudinal air-vacuum passageway through the collar anannular air-vacuum passageway intersecting the longitudinal passagewayand provided in the end of the sleeve member by a counterbore closed bythe confronting face of the collar in airtight sealed relation withrespect to the end of the sleeve member, said annular passageway beingin continuous communication with the first-named port in the hydraulicdisplacing member leading to said variable pressure chamber.

10. A brake operating mechanism constructed in accordance with claim 9including a vacuum passageway closed at one end by the engaging face ofthe collar, with the other end intersecting the second port in thehydraulic displacing member whereby, when the collar is separated fromthe sleeve member by operator force, power-assist from the servomotor isinactivated, the longitudinal passageway in the sleeve member is placedin communication with the variable pressure chamber to operativelyenergize the power assembly despite the separated status between thecollar and sleeve member, to restore normal engaging relationtherebetween.

11. A brake operating mechanism constructed in accordance with claim 7wherein said reaction means comprise: a hydraulic reaction memberslidably disposed in said tubular hydraulic displacing member with oneend engaging the valve piston and the other end being subjected to fluidpressure conditions in the master cylinder working chamber wherebyproportional hydraulic thrust reacts simultaneously on the valve pistonand operatoroperated link.

12. In a brake booster mechanism including a pressure fluid operatedservomotor having a casing provided with a movable wall actuated by apressure differential on opposite sides thereof, a hydraulic mastercylinder, a hydraulic fluid displacing member operable in said cylinderand connected with said wall for actuation thereby, follow-up valvemechanism having one position to establish balanced pressures onopposite sides of the wall to inactivate said servomotor and a secondposition to establish differential pressures on opposite sides of thewall to inactivate said servomotor, operator-operated means connectedwith said valve mechanism to operate the same between said two positionsto control said servomotor and engageable with the hydraulic displacingmember to operate the same directly and independently of said wall whenthe servomotor becomes inactivated, a normally preloaded spring reactingin said valve mechanism to establish the one position thereof, limitingmeans operatively associated with said valve mechanism to define the oneposition thereof, the improvement which comprises: mechanical releasablemeans for normally connecting said wall with said hydraulic displacingmember for movement together during power-activation of said servomotor,said lastmamed means incorporating a spring-loaded element movableagainst its spring load in response to movement of the hydraulicdisplacing member under operator actuation, to efiect disconnectionbetween said wall and hydraulic displacing member to enable operation ofthe latter independently of said wall; and another normally preloadedspring of greater strength than the connecting elfect of saidspring-loaded element, reacting between a portion of said servomotorcasing and said wall to induce said disconnection to enable resetting ofthe latter in inactive position upon said servomotor becominginactivated at any activated position thereof.

References Cited in the file of this patent UNITED STATES PATENTS1,960,996 Guernsey May 29, 1934 2,185,264 Mistral Jan. 2, 1940 2,229,247Kamenarovic Jan. 21, 1941 2,241,374 Alfieri May 13, 1941 2,260,491Stelzer Oct. 28, 1941 2,365,471 Ingres Dec. 19, 1944 2,395,223 IngresFeb. 19, 1946 2,463,062 Seppmann Mar. 1. 1949 2,642,165 Banker June 16,1953 2,644,305 Price et al. July 7, 1953 2,683,352 Price July 13, 19542,685,170 Price Aug. 3, 1954 2,685,171 Price Aug. 3, 1954 2,685,172Price Aug. 3, 1954 2,690,740 Hupp Oct. 5, 1954 2,766,852 Ingres Oct. 16,1956 2,767,548 Ayers Oct. 23, 1956 2,800,770 Edge et a1 July 30, 19572,826,042 Rike et al. Mar. 11, 1958 2,852,921 Ayers Sept. 23, 1958FOREIGN PATENTS 747,273 France June 14, 1933 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 2 968 926 January 24V 1961 Glenn'l"e Randol It is hereby certified that error appears in the abovenumbered patent requiring correction and that the said Letters Patentshould read as corrected below.

Column 4 line 6, for "longitudnal" read longitudinal column 5 line 60after "in" insert commercial 3 column 6 line 29 strike out "to"; column9 line 8 for "are" read is --5 column 12, line 16 for "cylinder" readcylinders --5 column 14 lines 54 and 57, for 81% each occurrence read 82-j' column l6 line- 30 after "pedal" insert a comma; column 17., line 36the italicized "a" should be enclosed in quotation marks; line 36 for"exponent l to read exponent "l" to -3; column 18 line 45 for "1410"read 14 column l9 line l5 for "opopsite read opposite column 21,, line41,, for "relatively" read relative line 63 for "the first occurrenceread --"their column 22 line 8 for "nad" read and column 23 line 61after "cylinder" insert a comma; column 25 line 38 for the head of theand face read the end face head column 26 line 35, after "comprises"insert a colon,,

Signed and sealed this 22nd day of May 1962,

(SEAL) Attest: ERNEST W. SWIDER DAVID L, LADD Attesting OfficerCommissioner of Patents

